I think your picture unites some smaller flawes that altogether led to a quality rejection.
First thing I can see is that the white parts of the fuselage are a bit overexposed, the sky is a bit grainy and while the wingtip is nice and sharp, the belly looks a bit soft (out of focus).
I can also see a lot of green and purple halos, especially on the lower part of the fuselage.
Another thing that looks awkward to me is your crop, but that's a matter of personal taste.